1) Field of the Invention
This invention relates to an electrically programmable read only memory (EPROM) device and a method of making this device which has high efficiency of electron injection to the floating gate.
2) Description of the Prior Art
The channel hot electron (CHE) injection transistor with step split was described and claimed in Seiki Ogura U.S. Pat. No. 5,780.341. The effective horizontal channel length under the floating gate of that U.S. Patent was designed to be very short.
M. Kamiya et al "EEPROM Cell With High gate injection Efficiency" published in IEDM, 1982, page 741 describes conventional split gate source-side injection transistor.
Y. Yamauchi, "A 5V-Only Virtual Ground Flash Cell with An Auxiliary Gate for High Density and High Speed Application", published in IEDM 1991, page 11.7.1 describes a Flash EEPROM device and method for making the device. The memory device seems similar to the present invention, but is structurally different and the method for fabricating is much different. Further, the device cannot give the efficiency of electron injection from channel to floating gate that is possible in the present invention.